This file provides NOP-compatible hint functions for devices using the ARMv6-M, ARMv7-M, and ARMv8-M instruction sets.
Source:
ARMv6-M Architecture Reference Manual A6.6 Hint Instructions https://developer.arm.com/documentation/ddi0419/e
procedure Send_Event
A6.7.57 SEV
Causes an event to be signaled to all CPUs within a multiprocessor system.
procedure Wait_For_Event
A6.7.75 WFE
Permits the processor to enter a low-power state until one of a number of events occurs, including events signaled by the SEV instruction on any processor in a multiprocessor system.
procedure Wait_For_Interrupt
A6.7.76 WFI
Suspends execution until one of a number of events occurs.
procedure Yield
A6.7.77 YIELD
Enables software with a multithreading capability to indicate to the hardware that it is performing a task, for example a spinlock, that could be swapped out to improve overall system performance. Hardware can use this hint to suspend and resume multiple code threads if it supports the capability.